Project/project/Start.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace project
{
    public partial class Start : Form
    {
        public Start()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            this.Hide();
            Vhod Vhod = new Vhod();
            Vhod.Show();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Hide();
            Registr Registr = new Registr();
            Registr.Show();
        }

        private void Start_FormClosed(object sender, FormClosedEventArgs e)
        {
            Application.Exit();
        }

    }
}